The mother-offspring relationship is the key determinant of offspring survival and reproductive success in most mammals, including humans. Understanding the behavioral and proximate means through which matemal behavior Influences offspring success therefore has a long research history but studies are understandably biased towards captive populations. While elegant captive work demonstrates the transmission of maternal behavior and stress physiology across generations, they lack the ful! extent of environmental heterogeneity that is a critical part of the dynamic behavior-physiology-environment axis. This research fills that gap by investigating the interplay between matemal behavior and stress physiology in wild chimpanzees for the first time. In particular, this study integrates an unrivaled 40-year behavioral dataset with new behavioral, physiological, and health data to: 1) investigate the relationship between maternal stress and behavior, 2) investigate the relationship between maternal behavior and offspring health, stress, and development, and 3) test how short-term fitness consequences of maternal behavior act across generations. These aims will be addressed amorig the chimpanzees at Gombe National Park, the longest, continuous chimpanzee study site in the world. To address these aims, long-term data analysis is paired with new multiple day family follows which include the collection of detailed behavioral data and fecal samples. Fecal samples are used to extract stress hormones, quantify parasite loads, and measure immune function. This approach allows maternal behavior to be linked directly to offspring physiological and health outcomes. The results ofthis study will yield a functional understanding ofthe complex mother-infant relationship and hgw it works across generations; that is, it will parse out which parts ofthe family systern are important in the short-term from those that have long-term consequences for reproductive success. Understanding this in chimpanzees will have direct application to the same topic in humans.